Does light from a transparent bottle cause instability of lotion?

I have made a moisturizer based on petrolatum and glycerin. The price is low and my competitors are also low price moisturizers. If i use jar or tube the cost will increase a lot. The inexpensive option is transparent PET bottle. My question is

Does light from a transparent PET bottle cause instability of lotion? 


  • Hello @Abdullah.

    Well, I think you already know the answer to this one. Transparent bottles of any kind tend to be worse at keeping the product stable compared to for example, medical amber glass or non-transparent airless bottles. But, what can you do providing that you really don't have the choice?

    -Add some EDTA, BHT, mixed tocopherols and proper preservative to your formula
    -On label explicitly leave a note to keep the product away from direct sunlight
    -Use non-transparent label and make so it covers most of the transparent package (believe it or not this actually helps in a great manner) and
    -Leave the product in intented package 21 day at room temperature and on direct sunlight. Observe what happens with and without the label, with different amount of antioxidant and etc. 
  • @Svemirska_baklava thanks a lot.

    Can i ask why 21 days? 
  • Well, there isn't anything specific about 21 days really. We always used 3 to 5 weeks for stability testing in my University, presumably bc to get some reproductive results in the smallest time possible.
    So, by leaving the product for 3 weeks on direct sunlight you can effectively reproduce the stability of formulation for up to 1 year, and that can be more then enough to evaluate. Or course, doing stress tests for cosmetics products is always the best way of obtaining good results for stability, but they tends to be costly and time consuming, especially for your application. 
  • As long as you use the right amount of chelators, antioxidants and preservatives I think you gonna be just fine. :) 
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